Optical communications systems facilitate high-speed and high-bandwidth data transmission over short and long distances (e.g., from a few hundred meters within a datacenter to thousands of meters of underwater fiber). One type of optical communication system for transmitting data over long distances is known as a long-haul optical communication system. In long-haul optical communication systems, data rates are increased by employing coherent optical transmissions, in which data may be modulated onto amplitudes, phases, and/or polarization components of an optical carrier signal. In these long-haul optical communication systems, the performance may be limited by fiber optic impairments such as chromatic dispersion (CD), local oscillator frequency offset (LOFO), polarization mode dispersion (PMD), phase noise, non-linear effects, and mixing of dual-polarization X and Y data streams due to time-varying state of polarization (SOP) rotations.
Often, these impairments are compensated for through digital signal processing in a mixed time and frequency domain approach (e.g., using a frequency domain to compensate for CD and using a time-domain equalizer to compensate for the mixed X and Y data streams). However, as a number of taps in the time-domain equalizer increases, the mixed time and frequency domain approach increases in complexity. Therefore, a single-domain approach to compensating for these impairments is desirable.